There was a recent post on a steam powered aircraft from the 1930s. And another recent one on miniature air powered engines. I was just wondering, with modern technology, is either one really viable as an aircraft engine? For air, you would need a large pressure tank in order to get any range at all. And a way to fill it if you are away from your home base. Or a compressor on board and some way to power that. For steam, you need a boiler and a water supply. And fuel for the boiler. Seems to me that neither would be any where as near efficient as a good ole' IC engine running on av gas. The only advantage I see is that the engine itself could be lighter because you would not have to deal with the N explosions every revolution, with resulting heat and pressures. By the way, the Tucker automobile comes to mind. If I recall correctly, it was air powered with a small gas powered compressor in the trunk. I don't know how well that would work when scaled up for aircraft use.